1. Field of the Invention
The present invention relates to an ultrasound therapy apparatus for applying an ultrasonic beam to a calculus or a tumor, and more particularly, to an apparatus for displaying a tomogram of a region of interest (ROI) of a patient, and for setting, with reference to the tomogram, an applicator (e.g., an ultrasonic beam emitter) in such a position that the beam emitted therefrom is precisely focused on the calculus or tumor present in the ROI.
2. Discussion of Background
With a therapy apparatus for applying an ultrasonic beam to disintegrate a calculus, it is necessary to focus the beam exactly on the calculus in order to effectively disintegrate it without damaging the tissues in the close vicinity thereof. Hence, the applicator for emitting the beam must be set in such a position that the beam emitted is sharply focused on the calculus itself. To correctly position the applicator, a tomogram of the ROI must be displayed to help a doctor ascertain the exact location of the calculus.
Japanese Patent Disclosure (Kokai) No. 59-101143 discloses a therapy apparatus comprising an ultrasonic beam emitter and two ultrasonic transducers. The beam emitter emits an ultrasonic beam to disintegrate a calculus. The transducers are used to form and display, in two selected, intersecting planes, the images of the region of interest. By examining these images (i.e., the two tomograms), the doctor can ascertain the precise location of the calculus. However, since the operator cannot clearly determine the exact location at which the emitted beam is focused, he or she cannot move the beam emitter to ensure that the ultrasonic beam is sharply focused on the calculus.
European Patent Publication No. 0148653 discloses an ultrasound therapy apparatus comprising a main piezoelectric transducer with an auxiliary piezoelectric transducer secured thereto. The main transducer is used to emit an ultrasonic beam for disintegrating a calculus, and the auxiliary transducer is provided to form a tomogram of the ROI in which the calculus has been found. The main transducer is supported by a support device which is used to move the main transducer along the X, Y, and Z axes which intersect with one another at the right angles. The apparatus further comprises a display device for displaying the tomogram and a cross for indicating the theoretical focal point of the main piezoelectric transducer. The operator operates the support device in the X direction, thus moving the main transducer in the X direction until the cross appears on the screen of the display device. Then, he or she operates the support device in the Y and Z directions, thereby moving the main transducer in the Y and Z directions until the cross is positioned at the center of the image of the calculus displayed on the screen. In this way, the main piezoelectric transducer can be set at its optimum position.
Even so, it is time-consuming to move the image of the calculus into the field of view of the auxiliary piezoelectric transducer, for the two reasons.
First, the display device displays only one tomogram.
Secondly, the calculus moves as the patient breathes or moves.
Further, since only one tomogram is displayed, the operator cannot visualize a stereoscopic image of the calculus, and thus cannot know with certainty whether or not the calculus has been throughly disintegrated. In most cases, a calculus is not crushed to the same extent in all directions when an ultrasonic beam is applied to it. Accordingly, even if one tomogram of the ROI suggests that the calculus has been disintegrated to a sufficient extent in one direction, it may not have been disintegrated to the same extent in another direction. In this case, the doctor may mistakenly believe that the calculus has been completely disintegrated and thus may take no further remedial action.